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Author Topic: I want to know why don't cis-trans isomer of cyclohexene exist?  (Read 10339 times)

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tree234

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I am studying mcmurry organic chemisty of 6th edition
When I start to study additional problems. I have some problem of one question
The qustion want to expailn about why don't cyclohexene have a cis-trans isomer, but cyclodecene does?
I try to find the answer about this question on the internet.
I just get cyclodecene is so big enough to exist trans-cyclodecene, but cyclohexene dosen't. I can't understand just small explin about this question.
Someone help me to understand about this. Plz, recount about this question.
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lemonoman

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Re:I want to know why don't cis-trans isomer of cyclohexene exist?
« Reply #1 on: August 02, 2005, 05:09:44 PM »

Check out the pictures rleung drew and posted on this similar thread:

http://www.chemicalforums.com/index.php?board=3;action=display;threadid=3855

Hopefully that shows you the cis/trans-iness of cyclodecene.

Notice the way the molecule is bent.  Can cyclohexene do anything like THAT to get a trans isomer?
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laotree

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Re:I want to know why don't cis-trans isomer of cyclohexene exist?
« Reply #2 on: August 08, 2005, 05:03:06 PM »

Trans hexene? How great should the strain be? :)
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alphahydroxy

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Re:I want to know why don't cis-trans isomer of cyclohexene exist?
« Reply #3 on: August 09, 2005, 03:33:47 AM »

Yep - the strain would be too great.

It is simply because the size of the ring cannot accomodate a trans double bond within it.

You could make a model (or draw it out, remembering to keep your bond angles reasonable). build the trans alkene unit, and try and build the ring around it - you'll have some trouble....

Now, if you try this with decene, you'll find it much easier.
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